This invention relates to a method of producing a defoamer composition.
The foaming of a liquid presents a serious problem in a variety of industrial processes including the treatment of the liquid itself or the treatment of something else by the liquid. The foaming of the liquid brings about a reduction in the efficiency of the treatment or a lowering in the quality of the product to be manufactured.
It is known that the problem of foaming may be solved by a defoamer having the effect of breaking foam in a liquid or inhibiting or reducing its foamability. A silicone defoamer is particularly suitable, since it is chemically stable and hardly has an influence on the liquid to which it is applied, and its use in a very small quantity produces a relatively large defoaming effect.
Various types of silicone defoamers have hitherto been proposed and are known. For example, Japanese Patent Publication No. 23613/1970 describes a defoamer composition composed of dimethylpolysiloxane oil, a specific siloxane resin and silica aerogel. Japanese Patent Publication No. 1602/1972 describes a defoamer composition obtained by heating polyorganosiloxane with a finely powdered additive, such as silica, in the presence of an alkaline substance. The known silicone defoamers have, however, the disadvantage that their defoaming effect, particularly their foam inhibiting effect, lasts only for a short period of time and fails to satisfy the requirement of a process in which it is necessary to inhibit foam for a long period of time.
Under these circumstances, it is an object of this invention to provide a method of producing a defoamer composition which maintains an excellent foam inhibiting effect for a long period of time.